Berghia nudibranchs are the ones that eat aiptasia. once your problem is gone, you can just sell/pass them along to someone with the same problem or trade them in at a LFS. It's not hard to find people willing to buy them since aiptasia is such a common occurence. Peppermint shrimp do a pretty good job, but if you have any really large ones, it's a good idea to use an aiptasia control product to nuke those, because IME, they don't really mess with the big ones.